1. Field of the Invention
This invention relates to a copying apparatus provided with an automatic original feeding device for automatically feeding an original to an exposure position.
2. Description of the Prior Art
In a conventional copying apparatus having an automatic original feeding device, where an original is placed at an exposure position, if a copy start instruction is effected, discharge of the original at the exposure position is inhibited and the next original is fed to a feeding position to cause jam of the original and damage the original or the original at the exposure position is discharged and the next original is fed to the exposure position without the first original at the exposure position being copied. This has required the user to carry out a very cumbersome procedure of returning the discharged original to the original feeding position.
Also, in the past, when interruption of the operation of the copying apparatus body has been instructed, only the portion of the apparatus which is concerned with image formation has been stopped with the original left at the exposure position. Since the user effects the interruption instruction when the original at the exposure position is not necessary, it has been a cumbersome procedure to take the original out of the automatic feeding device.
Generally, a copying apparatus having the automatic original feeding function of automatically feeding sheet-like originals has the ordinary copying function of effecting exposure with a thick original such as a book or the like placed on an original supporting table so that such a thick original may also be copied. Heretofore, however, in such a copying apparatus, originals have been automatically fed even when the next user has placed, by mistake, the originals in a container portion for containing originals after copying has been terminated by automatic original feeding. This has led to wasteful copies or, when the original has not been properly placed, damaged originals.
Where originals of a relatively large size are fed, a sufficient feeding interval cannot be secured between an already copied original and the next original, so that jam tends to occur or such a situation occurs that the copied original has not yet been discharged copletely when the next original has been set to the exposure position. To avoid such situation, it would occur to mind to discharge the next original after the copied original has been discharged, but if this was done, the feeding interval would widen so much that no improvement in copying speed could be expected.
Generally, in a copying apparatus or the like wherein copying is effected with an original placed on an original supporting surface, the original must be positioned because it must be placed at a predetermined exposure area on the original supporting surface. This is because the exposure area for each original size (for example, A4 or B4) is determined on the original supporting surface 101 (see FIG. 8) and if an original is placed in deviated relationship with such exposure area, the image of the original as so deviated is copied on copy paper and the information of the original fails to be copied at an accurate position. In such case, positioning of the original is usually accomplished by causing the original to bear against one end of the original supporting surface 101, for example, the end 102 of the original supporting surface 101 and a positioning plate 103 (FIG. 8).
However, in an automatic original feeding device for automatically feeding a plurality of sheet originals as shown in FIG. 9, the sheet originals are slidingly conveyed on the original supporting surface 101 and therefore, when the sheet original is so conveyed, the resistance thereof to the direction of conveyance differes, for some reason or other, between that side of the original which contacts the positioning plate 103 and the opposite side, so that the sheet original is moved obliquely or, when deviated from the conveyance path, the sheet original may touch any obstacle which may stand near the conveyance path, so that the oblique movement of the sheet original may be promoted or the sheet original may become wrinkled or even broken. In FIG. 8, when an original is conveyed in the direction of arrow 120 by the automatic original feeding device, the sheet original as conveyed may touch the original positioning plate 103 and this may lead to the danger of the sheet original being damaged as described above. Accordingly, no safety of the original is ensured in such a condition and therefore, the positioning plate 103 and the original must be kept apart from each other during the conveyance of the original. As a method therefor, it first occurs to mind to deviate the conveyance path of the sheet original from the positioning plate 103, but since the sheet original cannot be accurately placed at the exposure position, part of the information of the sheet original may fail to be copied. Secondly, if the positioning plate 103 is removed and the original supporting surface is printed with a positioning display line, the exposure position may be determined accurately but, when a thick original such as a book or the like which cannot be handled by the automatic original feeding device is to be copied, it becomes impossible or difficult to position the original by causing the original to bear against the end of the original supporting surface.
In such a copying apparatus as previously described, there is a glass platen on which an original may rest so that the original may be optically scanned. In an automatic original feeding device designed such that a thin original (usually, a sheet of about 30 g/m.sup.2) conveyed on such platen surface bears against stop pawls lowered to the platen surface and comes to a balt at a predetermined position, if the width of the stop pawls 202 and 203 is narrow as shown in FIG. 15a, the force acting on a unit length of the leading end of the original 201 which bears against the pawls is so great that the portion of the leading end of the original which bears against the pawls may become bulged or broken. In FIG. 15b, the original is designated by 201 and the stop pawls are designated by 202a and 203a. If the width of the stop pawls is increased, the force exerted on the portion of the original 201 which bears against the stop pawls is dispersed as shown in FIG. 15b, thus reducing the damage imparted to the leading end of the original. However, it is necessary to bring the stop pawls 202a and 203a having a great width into uniformly intimate contact with the platen surface. If the pawls are in intimate contact with the platen surface as shown in FIG. 16a, the leading end of the original can uniformly touch the entire width of the pawls, whereas if the pawl 202a is not in uniformly intimate contact with the platen surface 204 but obliquely touches such platen surface as shown in FIG. 16b, the original 201 will only touch a part of the pawls and the leading end of the original will be damaged for the reason set forth above.